"If you are discouraged because of your sinfulness, do not depend on your virtue or the strength of your case before God. Rather, depend entirely upon His mercy, for no one is righteous. We are all sinners. But this is not a cause for discouragement, for Christ came for sinners!" Quote Mark Mallet, see full article here.
I have a fault of falling pray to this sort of discouragement on a regular basis. I do not trust enough in God's mercy, but rather place too much emphasis on my own, very small strength to resist temptation. Lord, have mercy on me. I place my trust in You and depend upon your grace and mercy for my own salvation and that of my family.
Mary, Mother of God, be my salvation!